Leaning tank

[Scrappy71113]

My friend had to move and couldn't keep his tank. He gave it to me and I picked it up and set it up last weekend. I have come across the issue that it's leaning slightly forward. With my smaller tanks, I'm okay with this, I have never had any issues with it from my 75 gallon tanks or the smaller ones.
However, with this 100 gallon tank, I'm absolutely nervous that this isn't going to be sustainable long term.
The pictures below show the difference in water level between the front of the tank and back of the tank.
The logical side of my brain is like "it'll be fine, it's a minor issue, these things are made to hold the weight of crap tons of water, and this is a better quality tank than what you have had."
The anxious side of my brain is like "the front of this thing is going to blow out, fix it NOW!"
So, I would very much appreciate the opinions of the more knowledgeable and experienced people here.

Should I adjust the tank? Would shims work long term? Or is it okay and I can just leave it alone? It's a 3/8" difference between the front and back

 

[deeda]

I would fix it so it is level. Is this tank on carpet, if so it may be setting on the carpet tack that holds the carpet down near the wall.

 

[Scrappy71113]

I would fix it so it is level. Is this tank on carpet, if so it may be setting on the carpet tack that holds the carpet down near the wall.

It is on carpet. I'll move it out a bit to see if that fixes the issue.

 

[tlindsey]

It is on carpet. I'll move it out a bit to see if that fixes the issue.

If that doesn't work use a shim.

 

[duanes]

I always uses shims in my basement in the states, for a much smaller slant than I accept today.
I now live on an island (an itriangular rock) where any tanks I have are on a slant .
Below, a 125 gal sump

Below, a 180 gal

I am amazed both survived a 6.5 earthquake the other day.
I'm on a little white dot just right of the lower left point of the IGC triangle

 

[jjohnwm]

If the tank is merely tilted left/right or front/back, I don't think it's a big deal. I would fix it just because I have enough OCD that looking at it would drive me crazy, but I know guys with tanks set up that way for years that have had no issues.

The problem arises when the tank is not supported on a three-dimensionally flat surface; i.e. not just tilted but also "twisted" or torqued like a four-legged table with one short leg. The uneven forces applied to the seams in a case like that can and do cause failures, either simple leaks or spectacular blowouts; the same guys with the tilted tanks have proved this to me. I have helped clean up after one such catastrophic failure; you don't want that.